It takes 15 minutes to fill a large water tank. However, the tank has a small leak that would completely drain the tank in 4 hours. How long will it take to fill the tank if the leak is not plugged?
4 hours = 240 minutes. So, the fraction of the tank filled in one minute is
1/15 - 1/240 = 15/240 = 1/16
So, it will take 16 minutes to fill the leaking tank